多孔介质对圆柱-翼型干涉噪声的影响

Effects of porous media on rod-airfoil interaction noise

采用LES(large eddy simulation)+FW-H(Ffowcs Williams-Hawkings)方程,研究了圆柱表面使用不同PPI(pore number per inch)和厚度的多孔介质对圆柱尾迹及圆柱-翼型干涉噪声的影响,探索了多孔介质的降噪规律和机理。结果表明:多孔介质能稳定圆柱表面的剪切层,抑制旋涡脱落,从而削弱尾迹对下游翼型的影响,圆柱单音噪声最大可降79 dB,翼型单音峰值降低13.22 dB,宽频噪声降低20 dB;多孔材料PPI的变化对降噪效果影响较小,而厚度是影响流场模态、降噪效果及气动性能的一个关键参数;多孔材料厚度合适时,圆柱-翼型流场形态为“剪切层模态”,可有效降低湍流干涉噪声;多孔材料厚度较小时,发现了一种流场形态,即“剪切层-尾迹模态”,导致翼型噪声增大;合适的多孔介质厚度不仅降噪效果显著,对圆柱-翼型的气动性能也有改善作用。

Using LES(large eddy simulation)and FW-H(Ffowcs Williams-Hawkings)equation,the influences of porous media with different PPI(pore number per inch)and thicknesses on the cylindrical wake and rod-airfoil interaction noise were studied,and the noise reduction law and mechanism of porous media were explored.The results showed that the porous media can stabilize the shear layer on the surface of the cylinder,inhibit the vortex shedding,and weaken the impact of wake on the downstream airfoil.The maximum tonal noise of the rod can be reduced by 79 dB,the peak value of the tonal noise of the airfoil can be reduced by 13.22 dB,and the broadband noise can be reduced by 20 dB.The change of porous material PPI had little effect on the noise reduction effect,while the thickness served as a key parameter affecting the flow field mode,noise reduction effect and aerodynamic performance.When the thickness of the porous material was appropriate,the flow field of the rod-airfoil was of“shear layer mode”,which can effectively reduce the turbulent interaction noise.When the thickness of the porous material was small,a flow field form“shear layer-wake mode”was found,which caused the increase of airfoil noise.The appropriate thickness of porous media can not only reduce noise significantly,but also improve the aerodynamic performance of rod-airfoil.